Toys & mechanisms

Oldham Coupling Fidget — Offset-Shaft Constant-Velocity Demo Toy

A desk fidget that demos the Oldham coupling: spin the bottom knob and the top knob tracks it 1:1 even though the two shafts are parallel but laterally offset. A floating middle disc carries the rotation while its centre orbits a little circle. Five printed parts (4 unique designs), all flat and supportless. Useless, just fun.